National Physical Therapy Examination (NPTE) Practice Exam

What is the primary action of nitrates when prescribed for angina?

1. Decrease cardiac preload and decrease cardiac afterload

2. Decrease cardiac preload and increase cardiac afterload

3. Increase cardiac preload and decrease cardiac afterload

4. Increase cardiac preload and increase cardiac afterload

The correct answer is: Decrease cardiac preload and decrease cardiac afterload

Nitrates are primarily prescribed for angina due to their ability to act as vasodilators. They predominantly decrease cardiac preload by causing venodilation, which lowers the volume of blood returning to the heart. This reduction in venous return decreases the workload on the heart, making it easier for the heart to pump and reducing oxygen demand. Additionally, nitrates may cause some degree of decreased cardiac afterload due to arterial dilation, although the primary action is more significantly related to preload reduction. By decreasing preload and potentially affecting afterload, nitrates help alleviate the symptoms of angina by improving blood flow to the heart muscle and reducing the heart’s oxygen requirements during episodes of ischemia. Thus, the overall effect of nitrates makes them effective in managing angina pectoris by reducing the stress on the heart during activities that might otherwise provoke an angina attack.